Herbicidal quinoxaline carboxylic acid derivatives

ABSTRACT

The invention concerns novel compounds of the formula I ##STR1## The compounds are herbicides and in further embodiments the invention provides processes for the preparation of compounds of formula I, intermediates useful in the preparation of compounds of formula I, herbicidal composition containing as active ingredient a compound of formula I, and processes for severely damaging or killing unwanted plants by applying to the plants or to the growth medium of the plants an effective amount of a compound of formula I.

This invention relates to organic compounds having biological activity and in particular to organic compounds having herbicidal properties, to processes for the preparation of such compounds, to intermediates useful in the preparation of such compounds and to herbicidal compositions and processes utilizing such compounds.

We have now found a new class of quinoxalines which exhibit biological activity, and in particular herbicidal activity.

Accordingly the invention provides a compound of formula I: ##STR2## or a salt thereof wherein: A, B, D, E, J, U and V are independently chosen from the group consisting of hydrogen, halogen, nitro, cyano, thiocyano, amino, C₁ to C₆ alkylamino, di(C₁ to C₆ alkyl)amino, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl, C₂ to C₆ alkenyl, C₃ to C₇ cycloalkyl, C₁ to C₆ alkoxy, C₁ to C₆ haloalkoxy, C₁ to C₆ alkylthio, C₁ to C₆ alkylsulfinyl, C₁ to C₆ alkylsulfonyl, C₁ to C₆ haloalkylsulfinyl, C₁ to C₆ haloalkylsulfonyl, sulfo, C₁ to C₆ alkoxysulfonyl, sulfamoyl, N-(C₁ to C₆ alkyl)sulfamoyl, N,N-di(C₁ to C₆ alkyl)sulfamoyl, carboxy, (C₁ to C₆ alkoxy)carbonyl, carbamoyl, N-(C₁ to C₆ alkyl)carbamoyl, N,N-di(C₁ to C₆ alkyl)carbamoyl, phenyl, phenoxy, phenylthio, and the groups substituted phenyl, substituted phenoxy and substituted phenylthio wherein in each group the phenyl ring is substituted with from 1 to 3 substituents chosen from the group consisting of halogen, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl, C₁ to C₆ alkoxy, nitro and cyano;

R¹ is chosen from the group consisting of hydrogen, C₁ to C₁₀ alkyl, C₂ to C₁₀ alkenyl, C₂ to C₁₀ alkynyl, C₂ to C₁₀ alkoxyalkyl, cyanomethyl, (C₁ to C₆ alkoxy)carbonylmethyl, C₁ to C₁₀ haloalkyl, formyl, C₂ to C₁₀ alkanoyl, phenyl, benzyl, benzoyl, and the groups phenyl, benzyl and benzoyl wherein in each group the phenyl ring is substituted with from 1 to 3 substituents chosen from the group consisting of halogen, C₁ to C₆ alkyl, C₁ to C₆ halo-alkyl, C₁ to C₆ alkoxy, nitro and cyano;

R² is chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, C₂ to C₆ alkenyl, C₂ to C₆ alkoxyalkyl, C₁ to C₆ haloalkyl, acetyl, propionyl and C₂ to C₆ alkoxycarbonyl;

R³ is chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, C₂ to C₆ alkenyl, C₂ to C₆ alkoxyalkyl and C₁ to C₆ haloalkyl, or R² and R³ together may form a methylene, ethylidene, propylidene or isopropylidene group;

W is chosen from the group consisting of cyano, thiocarbamoyl ##STR3## and CH₂ Z wherein: G is chosen from the group consisting of hydroxy, mercapto, C₁ to C₁₀ alkoxy, C₁ to C₁₀ haloalkoxy, C₂ to C₁₀ alkenyloxy, C₂ to C₁₀ alkynyloxy, C₁ to C₁₀ alkylthio, C₂ to C₁₀ alkenylthio, C₂ to C₁₀ alkynylthio, C₃ to C₇ cycloalkoxy, C₃ to C₇ cycloalkoxy substituted with 1 or 2 C₁ to C₄ alkyl groups, phenoxy, phenylthio, benzyloxy, benzylthio, the group C₁ to C₆ alkoxy substituted with a substituent chosen from the group consisting of C₁ to C₆ alkoxy, amino, ammonio, cyano, N-(C₁ to C₆ alkyl)amino, N,N-di(C₁ to C₆ alkyl)amino and N,N,N-tri-(C₁ to C₆ alkyl) ammonio, the groups phenoxy, phenylthio, benzyloxy and benzylthio wherein in each group the phenyl ring is substituted with from 1 to 3 substituents chosen from the group consisting of halogen, nitro, cyano, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl and C₁ to C₆ alkoxy, the group OM wherein M is the cation of an inorganic or organic base, the group --NHSO₂ R⁴ wherein R⁴ is chosen from C₁ to C₁₀ alkyl and C₁ to C₁₀ haloalkyl, and the group --NR⁵ R⁶ wherein R⁵ and R⁶ are independently chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, C₁ to C₆ hydroxyalkyl, C₁ to C₆ haloalkyl, phenyl and benzyl, or R⁵ and R⁶ together form a heterocyclic ring, and the group --O--N═R¹⁰ wherein R¹⁰ is a C₁ to C₁₀ alkylidene group; and Z is chosen from halogen, hydroxy, mercapto, C₁ to C₁₀ alkoxy, C₁ to C₁₀ haloalkoxy, C₁ to C₁₀ alkylthio, and the group NR⁵ R⁶ wherein R⁵ and R⁶ are as hereinbefore defined;

X is chosen from oxygen and sulfur;

k and l are independently chosen from 0 and 1; and n is 0, 1 or 2.

The compounds of formula I wherein R² and R³ are not the same, are optically active and the present invention also includes the individual stereo isomers of such compounds, and mixtures of those stereo isomers in addition to the racemic mixture of stereo isomers.

Suitable A, B, D, E, J, U and V include hydrogen, halogen, nitro, cyano, thiocyano, amino, C₁ to C₆ alkylamino, di(C₁ to C₆ -alkyl)amino, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl, C₂ to C₆ alkenyl, C₃ to C₇ cycloalkyl, C₁ to C₆ alkoxy, C₁ to C₆ alkylthio, C₁ to C₆ alkylsulfinyl, C₁ to C₆ alkylsulfonyl, C₁ to C₆ -(alkoxy)carbonyl, phenyl, phenoxy, phenylthio, and the groups substituted phenyl, substituted phenoxy and substituted phenylthio wherein in each group the phenyl ring is substituted with from 1 to 3 substituents chosen from the group consisting of halogen, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl, C₁ to C₆ alkoxy, nitro and cyano.

Suitable R¹ include hydrogen, C₁ to C₁₀ alkyl, C₂ to C₁₀ alkenyl, C₂ to C₁₀ alkoxyalkyl, C₁ to C₁₀ haloalkyl, formyl, C₂ to C₁₀ alkanoyl, phenyl, benzyl, benzoyl, and the groups phenyl, benzyl and benzoyl wherein in each group the phenyl ring is substituted with from 1 to 3 substituents chosen from the group consisting of halogen, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl, C₁ to C₆ alkoxy, nitro and cyano.

Suitable R² include hydrogen, C₁ to C₆ alkyl, C₂ to C₁₀ alkenyl, C₂ to C₆ alkoxyalkyl, C₁ to C₆ haloalkyl, acetyl, propionyl, and C₂ to C₆ alkoxycarbonyl.

Suitable R³ include hydrogen, C₁ to C₆ alkyl, C₂ to C₆ alkenyl, C₂ to C₆ alkoxyalkyl and C₁ to C₆ haloalkyl, or R² and R³ together may form a methylene, ethylidene, propylidene or isopropylidene group.

Suitable W include cyano, thiocarbamoyl and the groups ##STR4## and CH₂ Z wherein: G is chosen from the group consisting of hydroxy, mercapto, C₁ to C₁₀ alkoxy, C₁ to C₁₀ haloalkoxy, C₁ to C₁₀ alkoxy substituted with C₁ to C₆ alkoxy, C₁ to C₁₀ alkylthio, C₂ to C₁₀ alkenyloxy, C₂ to C₁₀ alkynyloxy, C₂ to C₁₀ alkenylthio, C₃ to C₇ cycloalkoxy, C₃ to C₇ cycloalkoxy substituted with 1 or 2 C₁ to C₄ alkyl groups, phenoxy, phenylthio, benzyloxy, benzylthio, the groups phenoxy, phenylthio, benzyloxy and benzylthio wherein in each group the phenyl ring is substituted with from 1 to 3 substituents chosen from the group consisting of halogen, nitro, cyano, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl, and C₁ to C₆ alkoxy, the group OM wherein M is the cation of an inorganic or organic base, the group --NHSO₂ R⁴ wherein R⁴ is chosen from C₁ to C₁₀ alkyl and C₁ to C₆ haloalkyl, and the group --NR⁵ R⁶ wherein R⁵ and R⁶ are independently chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, phenyl and benzyl, or R⁵ and R⁶ together form a heterocyclic ring; and Z is chosen from halogen, hydroxy, mercapto, C₁ to C₁₀ alkoxy, C₁ to C₁₀ haloalkoxy, C₁ to C₁₀ alkylthio, and the group NR⁵ R⁶ wherein R⁵ and R⁶ are as hereinbefore defined.

Suitable k and l include 0.

Preferred A, B, D and E include hydrogen, halogen, nitro, cyano, amino, C₁ to C₆ alkylamino, di(C₁ to C₆ alkyl)amino, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl, C₂ to C₆ alkenyl, C₁ to C₆ alkoxy, C₁ to C₆ haloalkoxy, C₁ to C₆ alkylthio, carboxy and (C₁ to C₆ alkoxy)carbonyl.

Preferred J, U and V include hydrogen, halogen, nitro, cyano, C₁ to C₆ alkyl and C₁ to C₆ haloalkyl.

Preferred R¹ include hydrogen, C₁ to C₆ alkyl, C₂ to C₆ alkenyl, C₂ to C₆ alkynyl, benzyl, (C₁ to C₆ alkoxy)carbonylmethyl and cyanomethyl.

Preferred R² include hydrogen, C₁ to C₆ alkyl, C₂ to C₆ alkoxyalkyl and (C₁ to C₆ alkoxy)carbonyl.

Preferred R³ include hydrogen and C₁ to C₆ alkyl.

Preferred W include the groups:

(a) ##STR5## wherein G is chosen from the group consisting of hydroxy, C₁ to C₁₀ alkoxy, C₁ to C₁₀ haloalkoxy, C₂ to C₁₀ alkenyloxy, C₂ to C₁₀ alkynyloxy, C₁ to C₁₀ alkylthio, C₂ to C₁₀ alkenylthio, C₂ to C₁₀ alkynylthio, phenoxy, benzyloxy, cyclohexyloxy, the group C₁ to C₁₀ alkoxy substituted with a substituent chosen from the group consisting of C₁ to C₆ alkoxy, amino, N-(C₁ to C₆ alkyl)amino, N,N-di(C₁ to C₆ alkyl)amino and N,N,N-tri(C₁ to C₆ alkyl)ammonio, the group NR⁵ R⁶ wherein R⁵ and R⁶ are independently chosen from hydrogen, C₁ to C₆ alkyl, C₁ to C₆ hydroxyalkyl, C₁ to C₆ haloalkyl, and phenyl, the group OM wherein M is an alkali metal ion, alkaline earth metal ion or an ammonium ion HN.sup.⊕ R⁷ R⁸ R⁹ wherein R⁷, R⁸ and R⁹ are independently chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, C₁ to C₆ hydroxyalkyl, phenyl and benzyl, the group --NHSO₂ R⁴ wherein R⁴ is C₁ to C₆ alkyl, and the group --O--N═R¹⁰ wherein R¹⁰ is a C₁ to C₁₀ alkylidene group; and

(b) the group --CH₂ Z wherein Z is chosen from the group consisting of halogen, hydroxy, mercapto, C₁ to C₁₀ alkoxy, and the group --NR⁵ R⁶ wherein R⁵ and R⁶ are independently chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, C₁ to C₆ hydroxyalkyl, C₁ to C₆ haloalkyl and phenyl.

Preferred X is oxygen and preferred n is 0 or 2.

More preferably:

A, B, D and E are independently chosen from hydrogen, halogen, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl, nitro and cyano;

J, U and V are independently chosen from hydrogen and halogen;

R¹ is chosen from hydrogen and C₁ to C₆ alkyl;

R² is chosen from hydrogen and C₁ to C₆ alkyl;

R³ is chosen from hydrogen and C₁ to C₆ alkyl;

W is the group ##STR6## wherein G is chosen from hydroxy, C₁ to C₁₀ alkoxy, C₂ to C₁₀ alkenyloxy, C₂ to C₁₀ alkynyloxy, C₁ to C₁₀ alkylthio and the group OM wherein M is an alkali metal ion or an alkaline earth metal ion;

k and l are both 0; and

n is 0.

Examples of the compounds embraced by the invention include: ##STR7##

Preferred compounds of formula I are those compounds in which the phenyl ring is 1,4-substituted, that is compounds of formula II ##STR8##

Particular examples of compounds of the invention are detailed in Tables 1 and 2 below.

                  TABLE 1                                                          ______________________________________                                          ##STR9##                                                                      Com-                                                                           pound  Substituents                                                            No     A,B,D,E,J k      R.sup.1                                                                              R.sup.2                                                                              R.sup.3                                                                              G                                    ______________________________________                                         1      6-Cl      0      CH.sub.3                                                                             CH.sub.3                                                                             H     C.sub.2 H.sub.5 O                    2      3-Cl      0      CH.sub.3                                                                             CH.sub.3                                                                             H     C.sub.2 H.sub.5 O                    6      6,7-Cl.sub.2                                                                             0      CH.sub.3                                                                             CH.sub.3                                                                             H     C.sub.2 H.sub.5 O                    12     3,6,7-Cl.sub.3                                                                           0      CH.sub.3                                                                             CH.sub.3                                                                             H     C.sub.2 H.sub.5 O                    13     all H     0      CH.sub.3                                                                             CH.sub.3                                                                             H     C.sub.2 H.sub.5 O                    14     6-Cl      0      H     CH.sub.3                                                                             H     C.sub.2 H.sub.5 O                    15     6-NO.sub.2                                                                               0      CH.sub.3                                                                             CH.sub.3                                                                             H     C.sub.2 H.sub.5 O                    16     6-CH.sub.3                                                                               0      CH.sub.3                                                                             CH.sub.3                                                                             H     C.sub.2 H.sub.5 O                    17     6-Br      0      CH.sub.3                                                                             CH.sub.3                                                                             H     C.sub.2 H.sub.5 O                    18     6,7-(CH.sub.3).sub.2                                                                     0      CH.sub.3                                                                             CH.sub.3                                                                             H     C.sub.2 H.sub.5 O                    19     6-Cl      1      H     CH.sub.3                                                                             H     C.sub.2 H.sub.5 O                    20     7-CF.sub.3                                                                               0      CH.sub.3                                                                             CH.sub.3                                                                             H     C.sub.2 H.sub.5 O                    21     6-F       0      CH.sub.3                                                                             CH.sub.3                                                                             H     C.sub.2 H.sub.5 O                    22     7-CN      0      CH.sub.3                                                                             CH.sub.3                                                                             H     C.sub.2 H.sub.5 O                    23     6-Cl      0      CH.sub.3                                                                             H     N     C.sub.2 H.sub.5 O                    24     6-Cl      0      CH.sub.3                                                                             CH.sub.3                                                                             CH.sub.3                                                                             C.sub.2 H.sub.5 O                    25     6-Cl      0      CH.sub.3                                                                             C.sub.2 H.sub.5                                                                      H     C.sub.2 H.sub.5 O                    26     6-Cl      0      CH.sub.3                                                                             CH.sub.3                                                                             H     CH.sub.3 O                           27     6-Cl      0      CH.sub.3                                                                             CH.sub.3                                                                             H     HO                                   28     6-Cl      0      CH.sub.3                                                                             CH.sub.3                                                                             H     Na.sup.⊕ O.sup.⊖         29     6-Cl      0      CH.sub.3                                                                             CH.sub.3                                                                             H     n-C.sub.3 H.sub.7 O                  ______________________________________                                    

                  TABLE 2                                                          ______________________________________                                          ##STR10##                                                                     Compound     Substituents                                                      No           A,B,D,E,J   R.sup.1                                                                               G                                              ______________________________________                                         30           6-Cl        H      C.sub.2 H.sub.5 O                              31           6-Cl        CH.sub.3                                                                              C.sub.2 H.sub.5 O                              ______________________________________                                    

The compounds of the invention may be prepared by a variety of methods and in a further aspect the invention provides methods for the preparation of the compounds of formula I.

Compounds of formula Ia (I; ##STR11## wherein G is not hydroxy may be prepared from the acid of formula Ib (I; W=--CO₂ H) by, for example, neutralisation of the acid with a base to give an acid salt, esterification of the acid with an alcohol, thiol, phenol or thiophenol to give an acid ester, or reaction of the acid (or acid halide derivative thereof) with an amine to give an amide (SCHEME A). Processes known in the art for the preparation of acid salts, acid esters, acid halides and acid amides may be adapted, without undue experimentation, to prepare compounds of the invention of formula Ia from compounds of the invention of formula Ib. ##STR12##

Nitriles of the invention of formula Ic (I; W=--C.tbd.N) may be prepared, for example, from the acid amide of formula Id (I; W=--CONH₂) (SCHEME B). ##STR13##

Alcohols of the invention of formula Ie (I; W=CH₂ OH) may be prepared from the acid or acid esters of formula If (I; ##STR14## wherein G=OH or O-alkyl) by reduction (SCHEME C). Processes known in the art for the reduction of acids or acid esters to alcohols, for example lithium aluminium hydride reduction, may be adapted, without undue experimentation, to prepare alcohols of the invention of formula Ie from esters of the invention of formula If. ##STR15##

Alkyl halides of the invention of formula Ig (I; W=--CH₂ -halogen) may be prepared from alcohols of formula Ie (I; W=--CH₂ OH) by halogenation. Processes known in the art for the conversion of alcohols to alkyl halides, for example halogenation with reagents such as thionyl chloride, may be adapted, without undue experimentation, to prepare alkyl halides of the invention of formula Ig from alcohols of the invention of formula Ie.

Ethers of the invention of formula Ih (I; W=CH₂ OR) may be prepared from alcohols of formula Ie (I; W=--CH₂ OH) by alkylation. Processes known in the art for the conversion of alcohols to ethers, for example by reaction with alkyl halides using the Williamson ether synthesis, may be adapted, without undue experimentation, to prepare ethers of the invention of formula Ih from alcohols of the invention of formula Ie.

Ethers (thioethers) of the invention of formula Ih (Ii) [I; W=--CH₂ OR(--CH₂ SR)] may be prepared from alkyl halides of formula Ig (I; W=CH₂ -halogen) by alkoxylation (thioalkylation). Processes known in the art for the conversion of alkyl halides to ethers (thioethers), for example by reaction with alcohols (thiols) using the Williamson ether synthesis, may be adapted, without undue experimentation, to prepare ethers (thioethers) of the invention of formula Ih (Ii) from alkyl halides of the invention of formula Ig.

Amines of the invention of formula Ij (I; W=CH₂ NR⁴ R⁵) may be prepared from the alkyl halides of formula Ig (I; W=--CH₂ --halogen) by amination or from the amides of formula Ik ##STR16## by reduction. Processes known in the art for the conversion of alkyl halides to amines, for example by reaction with amines, and for the conversion of amides to amines, for example by reduction with agents such as lithium aluminium hydride, may be adapted without undue experimentation, to prepare amines of the invention of formula Ij from alkyl halides of the invention of formula Ig and from amides of the invention of formula Ik respectively.

N-oxides of the invention of formula I wherein one or more of k and 1 is 1 may be prepared from compounds of formula I wherein k and/or 1 is 0 by oxidation. Processes known in the art for the conversion of quinoxalines to quinoxaline N-oxides, for example oxidations using persulfates, peroxides, peracids or peresters, may be adapted without undue experimentation, to prepare the novel N-oxides of the invention.

Compounds of the invention of formula I wherein R¹ is not hydrogen may be prepared from compounds of the invention of formula I wherein R¹ is hydrogen by, for example, alkylation or acylation. Processes known in the art for the preparation of derivatives of secondary amines, for example alkylations with alkyl halides and acylations with acyl halides, may be adapted, without undue experimentation, to prepare the novel compounds of the invention wherein R¹ is not hydrogen.

Compounds of formula I wherein A, B, D, E, J, U, V, X, R¹, R², R³, W, k, l and n are as hereinbefore defined may be prepared by the condensation of a phenol or thiophenol of formula IX with a compound of formula X wherein hal is chlorine, bromine or iodine, preferably in the presence of an alkaline material; according to SCHEME D. ##STR17##

Compounds of formula I may also be prepared by:

(a) the condensation of the appropriate quinoxaline derivative of formula V, wherein L is a leaving group (for example, alkylsulfonyl, chlorine, bromine or iodine) with the appropriate aniline of formula VI according to SCHEME E. ##STR18## (b) the following steps in sequence: (i) the condensation of the appropriate quinoxaline derivative of formula V, wherein L is a leaving group (for example, alkylsulfonyl, chlorine, bromine or iodine) with the appropriate aniline of formula VII, wherein Q is hydroxy, mercapto, C₁ to C₆ alkoxy or C₁ to C₆ alkylthio to give a compound of formula VIII wherein Q is hydroxy, mercapto, C₁ to C₆ alkoxy or C₁ to C₆ alkylthio;

(ii) the dealkylation of the compound of formula VIII prepared in step (i) above wherein Q is C₁ to C₆ alkoxy or C₁ to C₆ alkylthio to give a compound of formula IX; and

(iii) the condensation of the product of formula IX obtained in step (i) or step (ii) above with a compound of formula X according to the process described for SCHEME D above (Steps (i) and (ii) are shown in SCHEME F); or

(c) the following steps in sequence:

(i) the condensation of the appropriate quinoxaline derivative of formula XI with the appropriate benzene derivative of formula XII wherein L is a leaving group (for example, alkylsulfonyl, chlorine, bromine or iodine) and Q is hydroxy, mercapto, C₁ to C₆ alkoxy or C₁ to C₆ alkylthio, to give a compound of formula VIII wherein Q is as hereinbefore defined;

(ii) the dealkylation of the compound of formula VIII prepared in step (i) above wherein Q is C₁ to C₆ alkoxy or C₁ to C₆ alkylthio, to give a compound of formula IX according to the process described for SCHEME F step (ii) above; and

(iii) the condensation of the product of formula IX obtained in step (i) or step (ii) above with a compound of formula X according to the process described for SCHEME D above (step (i) is shown in SCHEME G). ##STR19##

The condensation reaction illustrated in SCHEME D and outlined above is preferably carried out in the presence of an alkaline material and preferably in the presence of a solvent. Suitable alkaline materials include alkali metal and alkaline earth metal hydroxides and carbonates such as sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate. Suitable solvents include ketones such as, for example, acetone, methyl ethyl ketone and methyl isobutyl ketone, and dipolar aprotic solvents such as, for example, dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, hexamethylphosphoramide and sulfolan.

The condensation reactions illustrated in SCHEMES E and F and outlined above are preferably carried out in the presence of a solvent.

The reaction conditions required to effect the condensation reactions illustrated in SCHEMES D, E, F and G and outlined above vary according to the nature of the reactants and the solvent used. In general the reaction is facilitated by the application of heat and usually a reaction temperature in the range of 40° to 150° C. and reaction time of between 0.5 and 20 hours is satisfactory. However, higher or lower reaction temperatures and/or shorter or longer reaction times may be used if desired.

The dealkylation reactions illustrated in SCHEMES F and G and outlined in paragraphs (b) (ii) and (c) (ii) above may be effected using a variety of reagents known in the art. For example, aryl-alkyl ethers may be cleaved using reagents such as pyridine hydrochloride, hydriodic acid, hydrobromic acid, sodium thioethoxide in dimethylformamide, acetyl p-toluene-sulphonate, sodium or potassium iodide in formic or acetic acid, lithium iodide in 2,4,6-collidine and boron tribromide. Reaction times and reaction conditions vary widely depending on the dealkylation agent used and the ether to be cleaved. The reaction conditions generally employed when using the above "ether-cleavage" reagents are known to those skilled in the art and may be adapted without undue experimentation to effect the "ether-cleavage" reactions illustrated in SCHEMES F and G and outlined in paragraph (b) (ii) and (c) (ii) above.

The compounds of formula VIII ##STR20## which are useful intermediates in the preparation of compounds of formula I, are novel compounds. Therefore, in a further embodiment the invention provides compounds of formula VIII wherein A, B, D, E, k, l, J, R¹, U, V and Q are as hereinbefore defined.

The compounds of formula I are active as herbicides and therefore, in a further aspect the invention provides a process for severely damaging or killing unwanted plants which process comprises applying to the plants, or to the growth medium of the plants, an effective amount of a compound of formula I as hereinbefore defined.

Generally speaking the compounds of formula I are herbicidally effective against a variety of plants. However, certain of the compounds of the invention are selectively active against monocotyledonous plants, dicotyledonous plants being relatively unaffected by rates of application of the compounds of the invention which are severely damaging or lethal to other plant species.

Moreover, certain of the compounds of formula I are selectively active within the group of monocotyledonous plants and may be used at a rate sufficient to kill or severely damage monocotyledonous weeds in a monocotyledonous cereal crop.

Therefore, in yet a further aspect the invention provides a process for selectively controlling the growth of weeds in crops which process comprises applying to the crop, or to the growth medium of the crop, a compound of formula I, as hereinbefore defined, in an amount sufficient to severely damage or kill the weeds but insufficient to damage the crop substantially.

The compounds of formula I may be applied directly to the plant (post-emergence application) or to the soil before the emergence of the plants (pre-emergence application). However, the compounds are, in general, more effective when applied to the plant post-emergence.

The compounds of formula I may be used on their own to inhibit the growth of, severely damage, or kill plants but are preferably used in the form of a composition comprising a compound of the invention in admixture with a carrier comprising a solid or liquid diluent. Therefore, in yet a further aspect the invention provides plant growth inhibiting, plant damaging, or plant killing compositions comprising a compound of formula I as hereinbefore defined and an inert carrier therefor.

Compositions according to the invention include both dilute compositions, which are ready for immediate use, and concentrated compositions, which require to be diluted before use, usually with water. Preferably the compositions contain from 0.01% to 90% by weight of the active ingredient. Dilute compositions ready for use preferably contain from 0.01 to 2% of active ingredient, while concentrated compositions may contain from 20 to 90% of active ingredient, although from 20 to 70% is usually preferred.

The solid compositions may be in the form of granules, or dusting powders wherein the active ingredient is mixed with a finely divided solid diluent, e.g. kaolin, bentonite, kieselguhr, dolomite, calcium carbonate, talc, powdered magnesia, Fuller's earth and gypsum. They may also be in the form of dispersible powders or grains, comprising a wetting agent to facilitate the dispersion of the powder or grains in liquid. Solid compositions in the form of a powder may be applied as foliar dusts.

Liquid compositions may comprise a solution or dispersion of an active ingredient in water optionally containing a surface-active agent, or may comprise a solution or dispersion of an active ingredient in a water-immiscible organic solvent which is dispersed as droplets in water.

Surface-active agents may be of the cationic, anionic, or non-ionic type. The cationic agents are, for example, quaternary ammonium compounds (e.g. cetyltrimethylammonium bromide). Suitable anionic agents are soaps; salts of aliphatic mono esters of sulphuric acid, for example sodium lauryl sulphate; and salts of sulphonated aromatic compounds, for example sodium dodecylbenzenesulphonate, sodium, calcium, and ammonium lignosulphonate, butylnaphthalene sulphonate, and a mixture of the sodium salts of diisopropyl- and triisopropylnaphthalenesulphonic acid. Suitable non-ionic agents are the condensation products of ethylene oxide with fatty alcohols such as oleyl alcohol and cetyl alcohol, or with alkylphenols such as octyl- or nonyl-phenol or octyl- cresol. Other non-ionic agents are the partial esters derived from long chain fatty acids and hexitol anhydrides, for example sorbitan monolaurate; the condensation products of the partial ester with ethylene oxide; and the lecithins.

The aqueous solutions or dispersions may be prepared by dissolving the active ingredient in water or an organic solvent optionally containing wetting or dispersing agent(s) and then, when organic solvents are used, adding the mixture so obtained to water optionally containing wetting or dispersing agent(s). Suitable organic solvents include, for example, ethylene dichloride, isopropyl alcohol, propylene glycol, diacetone alcohol, toluene, kerosene, methylnaphthalene, the xylenes and trichloroethylene.

The compositions for use in the form of aqueous solutions or dispersions are generally supplied in the form of a concentrate containing a high proportion of the active ingredient, and the concentrate is then diluted with water before use. These concentrates are usually required to withstand storage for prolonged periods and after such storage, to be capable of dilution with water to form aqueous preparations which remain homogeneous for a sufficient time to enable them to be applied by conventional spray equipment. Concentrates conveniently contain 20-90%, preferably 20-70%, by weight of the active ingredient(s). Dilute preparations ready for use may contain varying amounts of the active ingredient(s) depending upon the intended purpose; amounts of 0.01% to 10.0% and preferably 0.1% to 2%, by weight of active ingredient(s) are normally used.

A preferred form of concentrated composition comprises the active ingredient which has been finely divided and which has been dispersed in water in the presence of a surface-active agent and a suspending agent. Suitable suspending agents are hydrophilic colloids and include, for example, polyvinylpyrrolidone and sodium carboxymethylcellulose, and the vegetable gums, for example gum acacia and gum tragacanth. Preferred suspending agents are those which impart thixotropic properties to, and increase the viscosity of the concentrate. Examples of preferred suspending agents include hydrated colloidal mineral silicates, such as montmorillonite, beidellite, nontronite, hectorite, saponite, and saucorite. Bentonite is especially preferred. Other suspending agents include cellulose derivatives and polyvinyl alcohol.

The rate of application of the compounds of the invention will depend on a number of factors including, for example, the compound chosen for use, the identity of the plants whose growth is to be inhibited the formulation selected for use and whether the compound is to be applied for foliage or root uptake. As a general guide, however, an application rate of from 0.005 to 20 kilograms per hectare is suitable while from 0.01 to 5 kilograms per hectare may be preferred.

The compositions of the invention may comprise, in addition to one or more compounds of the invention, one or more compounds not of the invention but which possess biological activity. For example, as hereinbefore indicated the compounds of the invention are in general substantially more effective against monocotyledonous plants or grass species than against dicotyledonous plants or broad-leaved species. As a result, in certain applications the herbicidal use of the compounds of the invention alone may not be sufficient to protect a crop. Accordingly in yet a still further embodiment the invention provides a herbicidal composition comprising a mixture of at least one herbicidal compound of formula I as hereinbefore defined with at least one other herbicide.

The other herbicide may be any herbicide not having the formula I. It will generally be a herbicide having a complementary action. For example, one preferred class is of mixtures comprising a herbicide active against broad-leaved weeds. A second preferred class is of mixtures comprising a contact herbicide.

Examples of useful complementary herbicides include:

A. benzo-2,1,3-thiadiazin-4-one-2,2-dioxides such as 3-isopropylbenzo-2,1,3-thiadiazin-4-one-2,2-dioxide (common name bentazon);

B. hormone herbicides and in particular the phenoxyalkanoic acids such as 4-chloro-2-methylphenoxyacetic acid (common name MCPA), 2-(2,4-dichlorophenoxy)propionic acid (common name dichlorprop), 2,4,5-trichlorophenoxyacetic acid (common name 2,4,5-T), 4-(4-chloro-2-methylphenoxy)butyric acid (common name MCPB), 2,4-dichlorophenoxyacetic acid (common name 2,4-D), 4-(2,4-dichlorophenoxy)butyric acid (common name 2,4-DB), 2-(4-chloro-2-methylphenoxy)propionic acid (common name mecoprop), and their derivatives (eg salts, esters, amides and the like);

C. 3-[4-(4-halophenoxy)phenyl]-1,1-dialkylureas such as 3-[4-(4-chlorophenoxy)phenyl]-1,1-dimethylurea (common name chloroxuron);

D. dinitrophenols and their derivatives (eg acetates) such as 2-methyl-4,6-dinitrophenol (common name DNOC), 2-tertiarybutyl-4,6-dinitrophenol (common name dinoterb), 2-secondarybutyl-4,6-dinitrophenol (common name dinoseb) and its ester dinoseb acetate;

E. dinitroaniline herbicides such as N', N'-diethyl-2,6-dinitro-4-trifluoromethyl-m-phenylenediamine (common name dinitramine), 2,6-dinitro-N,N-dipropyl-4-trifluoromethylaniline (common name trifluralin) and 4-methylsulfonyl-2,6-dinitro-N,N-dipropylaniline (common name nitralin);

F. phenylurea herbicides such as N'-(3,4-dichlorophenyl)-N,N-dimethylurea (common name diuron) and N,N-dimethyl-N'-[3-(trifluoromethyl)phenyl]urea (common name fluometuron);

G. phenylcarbamoyloxyphenylcarbamates such as 3-[(methoxycarbonyl)amino]phenyl (3-methylphenyl)carbamate (common name phenmedipham) and 3-[(ethoxycarbonyl)amino]phenyl phenylcarbamate (common name desmedipham);

H. 2-phenylpyridazin-3-ones such as 5-amino-4-chloro-2-phenylpyridazin-3-one (common name pyrazon);

I. uracil herbicides such as 3-cyclohexyl-5,6-trimethyleneuracil (common name lenacil), 5-bromo-3-sec-butyl-6-methyluracil (common name bromacil) and 3-tert-butyl-5-chloro-6-methyluracil (common name terbacil);

J. triazine herbicides such as 2-chloro-4-ethylamino-6-(iso-propylamino)-1,3,5-triazine (common name atrazine), 2-chloro-4,6-di(ethylamino)-1,3,5-triazine (common name simazine) and 2-azido-4-(iso-propylamino)-6-methylthio-1,3,5-triazine (common name aziprotryne);

K. 1-alkoxy-1-alkyl-3-phenylurea herbicides such as 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (common name linuron), 3-(4-chlorophenyl)-1-methoxy-1-methylurea (common name monolinuron) and 3-(4-bromo-4-chlorophenyl)-1-methoxy-1-methylurea (common name chlorobromuron);

L. thiolcarbamate herbicides such as S-propyl dipropylthiocarbamate (common name vernolate);

M. 1,2,4-triazin-5-one herbicides such as 4-amino-4,5-dihydro-3-methyl-6-phenyl-1,2,4-triazin-5-one (common name metamitron) and 4-amino-6-tert-butyl-4,5-dihydro-3-methylthio-1,3,4-triazin-5-one (common name metribuzin);

N. benzoic acid herbicides such as 2,3,6-trichlorobenzoic acid (common name 2,3,6-TBA), 3,6-dichloro-2-methoxybenzoic acid (common name dicamba) and 3-amino-2,5-dichlorobenzoic acid (common name chloramben).

O. anilide herbicides such as N-butoxymethyl-α-chloro-2',6'-diethylacetanilide (common name butachlor), the corresponding N-methoxy compound (common name alachlor), the corresponding N-iso-propyl compound (common name propachlor) and 3',4'-dichloropropionanilide (common name propanil);

P. dihalobenzonitrile herbicides such as 2,6-dichlorobenzonitrile (common name dichlobenil), 3,5-dibromo-4-hydroxybenzonitrile (common name bromoxynil) and 3,5-diiodo-4-hydroxybenzonitrile (common name ioxynil).

Q. haloalkanoic herbicides such as 2,2-dichloropropionic acid (common name dalapon), trichloroacetic acid (common name TCA) and salts thereof;

R. diphenylether herbicides such as 4-nitrophenyl 2-nitro-4-trifluoromethylphenyl ether (common name fluorodifen), methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate (common name bifenox), 2-nitro-5-(2-chloro-4-trifluoromethylphenoxy)benzoic acid and 2-chloro-4-trifluoromethylphenyl 3-ethoxy-4-nitrophenyl ether and the compounds disclosed in European Patent publication No. 3,416; and

S. miscellaneous herbicides including N,N-dimethyldiphenylacetamide (common name diphenamid), N-(1-naphthyl)phthalamic acid (common name naptalam) and 3-amino-1,2,4-triazole.

Examples of useful contact herbicides include:

T. bipyridylium herbicides such as those in which the active entity is the 1,1'-dimethyl-4,4'-dipyridylium ion (common name paraquat) and those in which the active entity is the 1,1'-ethylene-2,2'-dipyridylium ion (common name diquat);

U. organoarsenical herbicides such as monosodium methanearsonate (common name MSMA); and

V. amino acid herbicides such as N-(phosphonomethyl)glycine (common name glyphosate) and its salts and esters.

The invention is now illustrated by, but in no way limited to, the following Examples.

EXAMPLE 1 Ethyl 2-{4-[N-methyl-N-(6-chloro-2-quinoxalinyl)amino]-phenoxy}propionate (1)

(a) A mixture of 2,6-dichloroquinoxaline (1.0 g; prepared according to the method of A F Crowther et al J. Chem. Soc., 1949, 1260), 4-(N-methylamino)phenol sulfate (2.0 g), acetonitrile (50 ml) and water (50 ml) was heated under reflux for a period of 2 days. After cooling, 4-[N-methyl-N-(6-chloro-2-quinoxalinyl)amino]phenol was precipitated from the reaction mixture by the addition of water. Proton magnetic resonance spectrum (d₆ -acetone; δ in ppm): 8.3 (1H, s, quinoxaline hetero-ring proton); 7.8 (3H, m, quinoxaline benzo-ring protons); 7.2 (4H, m, phenoxy protons); 3.5 (3H, s, N--CH₃).

(b) A mixture of 4-[N-methyl-N-(6-chloro-2-quinoxalinyl)amino]phenol (4 mmole), ethyl 2-bromopropionate (1 ml), potassium carbonate (1.0 g) and butanone (100 ml) was heated under reflux for a period of 12 hr. The solvent was removed by distillation under reduced pressure and the residue was purified by column chromatography over silica gel (eluant dichloromethane/ethanol 98:2) to give ethyl 2-{4-[N-methyl-N-(6-chloro-2-quinoxalinyl)amino]phenoxy}propionate as an oil.

Proton magnetic resonance spectrum (CDCl₃ ; δ in ppm): 8.27 (1 H, s, quinoxaline hetero-ring proton); 7.0-8.0 (7 H, m, aromatic protons); 4.83 (1 H, q, CH--CH₃); 4.28 (2 H, q, CH₂ --CH₃); 3.50 (3 H, s, N--CH₃); 1.67 (3 H, d, CH--CH₃); 1.27 (3 H, t, CH₂ --CH₃).

EXAMPLE 2 Ethyl 2-{4-[N-methyl-N-(6,7-dichloro-2-quinoxalinyl)amino]phenoxy}propionate (6)

(a) A mixture of 4,5-dichloro-o-phenylenediamine (36.2 mmole) and alloxan monohydrate (36.2 mmole) in 10% aqueous acetic acid was stirred at room temperature for a period of 2 hours. Concentration of the reaction mixture gave N-(6,7-dichloro-2-hydroxy-3-quinoxalinoyl)urea which was added to 50% aqueous sulfuric acid and the mixture was heated at a temperature of 135° C. for a period of 3 hours. After cooling the precipitated material was collected by filtration, washed with water and then was slowly added to a 5% aqueous solution of sodium bicarbonate. The insoluble material was collected by filtration and was washed successively with water and ethanol to give 6,7-dichloro-2-hydroxyquinoxaline.

(b) Phosphorus oxychloride (50 ml) and phosphorus pentachloride (10 g) were added to 6,7-dichloro-2-hydroxyquinoxaline (6.6 g) and the mixture was stirred for a period of 1 hour. The mixture was then poured onto ice and the precipitate collected by filtration to give 2,6,7-trichloroquinoxaline, mp 137° C.

(c) 2,6,7-Trichloroquinoxaline was reacted with 4-(N-methylamino)phenol sulfate, following essentially the same procedure as that described in Example 1 Part (a), to give 4-[N-methyl-N-(6,7-dichloro-2-quinoxalinyl)amino]phenol. Proton magnetic resonance spectrum (d₆ -acetone; δ in ppm): 8.25 (1H, s, quinoxaline hetero-ring proton); 8.0 (1H, s, quinoxaline benzo-ring proton); 7.9 (1H, s, quinoxaline benzo-ring proton); 7.15 (4H, m, phenoxy protons; 3.55 (3H, s, N-CH₃).

(d) 4-[N-Methyl-N-(6,7-dichloro-2-quinoxalinyl)amino]phenol was reacted with ethyl 2-bromopropionate, following essentially the same procedure as that described in Example 1 Part (b), to give ethyl 2-{4-[N-methyl-N-(6,7-dichloro-2-quinoxalinyl)amino]phenoxy}propionate, mp 79° C. Proton magnetic resonance spectrum (CDCl₃ ; δ in ppm): 8.25 (1H, s, quinoxaline hetero-ring proton); 7.9 (1H, s, quinoxaline benzo-ring proton); 7.8 (1H, s, quinoxaline benzo-ring proton); 7.2 (4H, m, phenoxy protons); 4.85 (1H, q, CH-CH₃); 4.3 (2H, q, CH₂ -CH₃); 3.55 (3H, s, N-CH₃); 1.7 (3H, d, CH-CH₃); 1.3 (3H, t, CH₂ -CH₃).

EXAMPLE 3 Ethyl 2-{4-[N-Methyl-N-(3-chloro-2-quinoxalinyl)amino]phenoxy}propionate (2)

(a) 2,3-Dichloroquinoxaline (prepared according to the method of H M Woodburn, J. Org. Chem., 1958, 23, 262) was reacted with 4-(N-methylamino)phenol sulfate, following essentially the same procedure as that described in Example 1 Part (a), to give 4-[N-methyl-N-(3-chloro-2-quinoxalinyl)amino]phenol. Proton magnetic resonance spectrum (d₆ -acetone; δ in ppm): 7.5-8.1 (4H, m, quinoxaline protons); 7.1 (4H, m, phenoxy protons); 3.5 (3H, s, N-CH₃).

(b) 4-[N-Methyl-N-(3-chloro-2-quinoxalinyl)amino]phenol was reacted with ethyl 2-bromopropionate, following essentially the same procedure as that described in Example 1 Part (b), to give ethyl 2-{4-[N-methyl-N-(3-chloro-2-quinoxalinyl)amino]phenoxy}propionate as an oil.

Proton magnetic resonance spectrum (CDCl₃ ; δ in ppm): 7.5-8.2 (4H, m, quinoxaline protons); 7.0 (4H, m, phenoxy protons); 4.8 (1H, q, CH-CH₃); 4.3 (2H, q, CH₂ -CH₃); 3.5 (3H, s, N-CH₃); 1.65 (3H, d, CH-CH₃); 1.2 (3H, t, CH₂ -CH₃).

EXAMPLE 4 Ethyl 2-{4-[N-methyl-N-(3,6,7-trichloro-2-quinoxalinyl)amino]phenoxy}propionate (12)

(a) 2,3,6,7-Tetrachloroquinoxaline (mp 176° C.; prepared following essentially the same procedure as that referred to in Example 3 Part (a) for the preparation of 2,3-dichloroquinoxaline) was reacted with 4-(N-methylamino)phenol sulfate, following essentially the same procedure as that described in Example 1 Part (a), to give 4-[N-methyl-N-(3,6,7-trichloro-2-quinoxalinyl)amino]phenol.

Proton magnetic resonance spectrum (d₆ -acetone; δ in ppm); 7.9 (2H, m, quinoxaline protons); 6.9 (4H, m, phenoxy protons); 3.45 (3H, s, N-CH₃).

(b) 4-[N-Methyl-N-(3,6,7-trichloro-2-quinoxalinyl)amino]phenol was reacted with ethyl 2-bromopropionate, following essentially the same procedure as that described in Example 1 Part (b), to give ethyl 2-4-[N-methyl-N-(3,6,7-trichloro-2-quinoxalinyl)amino]phenoxy propionate as an oil.

Proton magnetic resonance spectrum (CDCl₃ ; δ in ppm): 8.0 (2H, m, quinoxaline protons); 7.1 (4H, m, phenoxy protons); 4.8 (1H, q, CH-CH₃); 4.3 (2H, q, CH₂ -CH₃); 3.5 (3H, s, N-CH₃); 1.65 (3H, d, CH-CH₃); 1.25 (3H, t, CH₂ -CH₃).

EXAMPLE 5

Compounds no 13, 15, 16, 17, 18, 20, 21 and 22 detailed in Table 1 were prepared from the appropriate quinoxaline, 4-(N-methylamino)phenol sulfate and ethyl 2-bromopropionate following essentially the same procedure as that described in Examples 1 to 4.

The structure assigned to each compound was confirmed by proton magnetic resonance spectroscopy and mass spectrometry and appropriate physical data is recorded in Example 14, Table 3.

EXAMPLE 6 Ethyl 2-{4-[N-(6-chloroquinoxalin-2-yl)amino]phenoxy}propionate (14)

(a) A mixture of 2,6-dichloroquinoxaline (10 mmole), 4-aminophenol (10 mmole), hydrochloric acid (10 mmole), acetonitrile (50 ml) and water (50 ml) was heated under reflux for a period of 3 days. After cooling 4-[N-(6-chloroquinoxalin-2-yl)amino]phenol was precipitated from the reaction mixture by the addition of water.

Proton magnetic resonance spectrum (d₆ -acetone; δ in ppm): 6.8-7.9 (7H, m, phenoxy protons and benzo-ring protons); 8.5 (1H, s, hetero-ring proton).

(b) A mixture of 4-[N-(6-chloroquinoxalin-2-yl)amino]phenol (10 mmole), ethyl 2-bromopropionate (10 mmole), anhydrous potassium carbonate (2.0 g) and methyl ethyl ketone (100 ml) was heated under reflux for a period of 12 hours. The mixture was filtered and the solvent was removed by distillation under reduced pressure. The residue was chromatographed over alumina (eluent dichloromethane) to give ethyl 2-{4-[N-(6-chloroquinoxalin-2-yl)amino]phenoxy}propionate, mp 136° C.

Proton magnetic resonance spectrum (CDDl₃ /d₆ -acetone; δ in ppm): 1.3 (3H, t, CH₂ -CH₃): 1.6 (3H, d, CH-CH₃); 4.3 (2H, q, CH₂ -CH₃); 4.8 (1H, q, CH-CH₃); 6.9-8.0 (7H, m, phenoxy and benzo-ring protons); 8.3 (1H, br s, NH); 8.5 (1H, s, hetero-ring proton).

EXAMPLE 7 Ethyl 2-{4-[N-(6-chloro-1-oxide-quinoxalin-2-yl)amino]phenoxy}propionate (19)

(a) Potassium persulfate (7.42 g) was slowly added to a stirred mixture of 2,6-dichloroquinoxaline (5.0 g) and concentrated sulfuric acid (25 ml) at a temperature of 10° C. On completion of the addition the mixture was allowed to warm to room temperature and the mixture was stirred for a further 24 hours. The mixture was poured into ice-water (400 ml), neutralized with aqueous sodium bicarbonate and the mixture was extracted with dichloromethane. The organic extract was washed with brine, dried (over anhydrous sodium sulfate) and the solvent was removed by distillation under reduced pressure. The residue was crystallised from ethanol to give 2,6-dichloroquinoxaline-1-oxide as brown needles, mp 185° C.

(b) A mixture of 2,6-dichloroquinoxaline-1-oxide (0.85 g), ethyl 2-(4-aminophenoxy)propionate (0.85 g), anhydrous sodium acetate (0.4 g), and ethanol (70 ml) was heated under reflux for a period of 44 hours. The mixture was filtered and the solvent was removed by distillation under reduced pressure. The residue was partitioned between ethyl acetate and water. The organic phase was separated, washed with water (2×200 ml), and dried over anhydrous sodium sulfate. The solvent was removed by distillation under reduced pressure and the residue was recrystallised from ethanol to give ethyl 2-{4-[N-(6-chloro-1-oxide-quinoxalin-2-yl)amino]phenoxy}propionate, mp 160° C.

Proton magnetic resonance spectrum (d₆ -acetone; δ in ppm): 1.2 (3H, t, CH₂ -CH₃); 1.6 (3H, d, CH-CH₃); 4.2 (2H, q, CH₂ -CH₃); 5.1 (1H, q, CH-CH₃); 6.9-8.8 (8H, m, aromatic ring protons); 10.0 (1H, s, NH).

EXAMPLE 8

Compounds no 23, 24, 25 and 26 detailed in Table 1 were prepared from 4-[N-methyl-N-(6-chloroquinoxalin-2-yl)amino]phenol and ethyl 2-bromoacetate, ethyl 2-bromo-2-methylpropionate, ethyl 2-bromobutyrate and methyl 2-bromopropionate, respectively, following essentially the same procedure as that described in Example 1 part (b).

The structure assigned to each compound was confined by proton magnetic resonance spectroscopy and mass spectrometry and appropriate physical data is recorded in Example 14, Table 3.

EXAMPLE 9 2-{4-[N-Methyl-N-(6-chloroquinoxalin-2-yl)amino]phenoxy}propionic Acid (27)

Methyl 2-{4-[N-methyl-N-(6-chloroquinoxalin-2-yl)amino]phenoxy}propionate (1.0 g; compound no 26, Example 8) was suspended in ethanol (5 ml) and a solution of sodium hydroxide (0.11 g) in water (5 ml) was added over a period of 45 minutes. Further ethanol (6 ml) was added and the mixture was stirred at room temperature for a period of 48 hours. The ethanol was removed by distillation under reduced pressure, the residue was dissolved in water and the aqueous solution was acidified to pH 4 by the addition of aqueous 2 M hydrochloric acid. The precipitate was collected by filtration and dried to give the title compound, mp 204° C.

Proton magnetic resonance spectrum (d₆ -dimethylsulfoxide; δ in ppm): 1.5 (3H, s, CH-CH₃); 3.45 (3H, s, NCH₃); 4.95 (1H, q, CH-CH₃); 7.0-7.9 (7H, m, phenoxy and benzo-ring protons); 8.2 (1H, s, hetero-ring proton).

EXAMPLE 10 Sodium 2-{4-[N-methyl-N-(6-chloroquinoxalin-2-yl)amino]phenoxy}propionate (28), mp 162° C., was prepared by the neutralization of the corresponding acid (compound no 27, Example 9) with aqueous sodium hydroxide and removal of the solvent under reduced pressure. EXAMPLE 11 n-Propyl 2-{4-[N-methyl-N-(6-chloroquinoxalin-2-yl)amino]phenoxy}propionate (29)

A mixture of 2-{4-[N-methyl-N-(6-chloroquinoxalin-2-yl)amino]phenoxy}propionic acid (2.0 g; compound no 27, Example 9) and thionyl chloride (25 ml) was heated under reflux for a period of 2 hours. The excess thionyl chloride was removed by distillation under reduced pressure to give 2-{4-[N-methyl-N-(6-chloroquinoxalin-2-yl)amino]phenoxy}propionyl chloride. A mixture of n-propanol (10 ml) and triethylamine (10 ml) was added and the mixture was stirred at room temperature for a period of 1 hour. The mixture was poured into water (200 ml) and the aqueous mixture was extracted with dichloromethane. The organic extract was washed several times with water and dried over anhydrous sodium sulfate. The solvent was removed by distillation under reduced pressure and the residue was chromatographed over alumina (eluent dichloromethane) to give n-propyl 2-{4-[N-methyl-N-(6-chloroquinoxalin-2-yl)amino]phenoxy}propionate as an oil.

Proton magnetic resonance spectrum (CDCl₃ ; δ in ppm): 0.9 (3H, t, CH₂ CH₂ CH₃); 1.75 (3H, d, CHCH₃); 1.8 (2H, m, CH₂ CH₂ CH₃); 3.5 (3H, s, NCH₃); 4.2 (2H, t, CH₂ CH₂ CH₃); 4.85 (1H, q, CHCH₃); 6.9-7.9 (7H, m, phenoxy and benzo-ring protons); 8.2 (1H, s, hetero-ring proton).

EXAMPLE 12 Ethyl 2-{3-[N-(6-chloroquinoxalin-2-yl)amino]phenoxy}propionate (30)

(a) A mixture of 2,6-dichloroquinoxaline (10 mmole), 3-aminophenol (20 mmole), sulfuric acid (10 mmole), acetonitrile (50 ml) and water (50 ml) was heated under reflux for a period of 12 hours. After cooling 3-[N-(6-chloroquinoxalin-2-yl)amino]phenol, mp 170° C., was precipitated from the reaction mixture by the addition of water.

Proton magnetic resonance spectrum (d₆ -acetone; δ in ppm): 6.9-9.5 (10H, m, aromatic protons, NH and OH).

(b) A mixture of 3-[N-(6-chloroquinoxalin-2-yl)amino]phenol (10 mmole), ethyl 2-bromopropionate (10 mmole), anhydrous potassium carbonate (2 g) and methyl ethyl ketone (100 ml) was heated under reflux for a period of 12 hours. The reaction mixture was filtered and the solvent was removed by distillation under reduced pressure. The residue was purified by chromatography over alumina (eluent dichloromethane) to give ethyl 2-{3-[N-(6-chloroquinoxalin-2-yl)amino]phenoxy}propionate as an oil.

Proton magnetic resonance spectrum (CDCl₃ ; δ in ppm): 1.2 (3H, t, CH₂ CH₃); 1.7 (3H, d, CHCH₃); 4.25 (2H, q, CH₂ CH₃); 4.95 (1H, q, CHCH₃); 6.7-9.45 (9H, m, aromatic ring protons and NH).

EXAMPLE 13 Ethyl 2-{3-[N-methyl-N-(6-chloroquinoxalin-2-yl)amino]phenoxy}propionate (31)

A mixture of ethyl 2-{3-[N-(6-chloroquinoxalin-2-yl)amino]phenoxy}propionate (10 mmole), sodium hydride (10 mmole), methyl iodide (50 mmole) and dimethylformamide (50 ml) was stirred at room temperature for a period of 3 hours. Water was added to the reaction mixture and the precipitated product was collected by filtration. The product was purified by chromatography over alumina (eluent dichloromethane) to give ethyl 2-{3-[N-methyl-N-(6-chloroquinoxalin-2-yl)amino]phenoxy}propionate as an oil.

Proton magnetic resonance spectrum (CDCl₃ ; δ in ppm): 1.2 (3H, t, CH₂ CH₃); 1.6 (3H, d, CHCH₃); 3.6 (3H, s, NCH₃); 4.3 (2H, q, CH₂ CH₃); 4.8 (1H, q, CHCH₃); 6.8-8.5 (8H, m, aromatic ring protons).

EXAMPLE 14

(a) A number of the compounds of the invention detailed in Tables 1 and 2 are solids and can be identified by melting point. Other compounds of the invention detailed in Tables 1 and 2 are oils and were characterised by, and can be identified by, their proton magnetic resonance (pmr) spectrum. For convenience, characterising data not already provided in Examples 1 to 13 is recorded in Table 3 below.

                  TABLE 3                                                          ______________________________________                                         Com-                                                                           pound Mp     Proton Chemical Shift                                             No    °C.                                                                            Solvent   δ in ppm                                          ______________________________________                                         13    Oil    CDCl.sub.3                                                                               1.3(3H,t,CH.sub.2 CH.sub.3); 1.7(3H,d,                                         CHCH.sub.3); 3.5(3H,s,NCH.sub.3); 4.3(2H,                                      q,CH.sub.2 CH.sub.3); 4.8(1H,q,CHCH.sub.3);                                    7.1(4H,m, phenoxy protons);                                                    7.4-8.0(4H,m, benzo ring)                                                      protons); 8.3(1H,s, hetero-ring                                                proton).                                                15    137    d.sub.6 -acetone                                                                         1.3(3H,t,CH.sub.2 CH.sub.3); 1.7(3H,d,                                         CHCH.sub.3); 3.6(3H,s,NCH.sub.3); 4.2                                          (2H,q,CH.sub.2 CH.sub.3); 5.0(1H,q,CHCH.sub.3);                                7.3(4H,m, phenoxy ring protons);                                               7.7-8.6(4H,m, quinoxaline ring                                                 protons).                                               16    Oil    d.sub.6 -acetone                                                                         1.2(3H,t,CH.sub.2 CH.sub.3); 1.6(3H,d,                                         CHCH.sub.3); 2.5(3H,s,CH.sub.3); 3.5(3H,                                       s,NCH.sub.3); 4.2(2H,q,CH.sub.2 CH.sub.3); 5.0                                 (1H,q,CHCH.sub.3); 7.0-7.7(7H,m,                                               phenoxy and benzo-ring protons);                                               8.1(1H,s, hetero-ring proton).                          17    Oil    d.sub.6 -acetone                                                                         1.2(3H,t,CH.sub.2 CH.sub.3 ); 1.6(3H,d,                                        CHCH.sub.3); 3.5(3H,s,NCH.sub.3); 4.2(2H,                                      q,CH.sub.2 CH.sub.3); 4.9(1H,q,CHCH.sub.3);                                    7.2(4H,m, phenoxy ring protons);                                               7.5-7.8(3H,m, benzo-ring                                                       protons); 8.0(1H,s, hetero-ring                                                proton).                                                18    Oil    d.sub.6 -acetone                                                                         1.15(3H,t,CH.sub.2 CH.sub.3); 1.55(3H,d,                                       CHCH.sub.3); 2.25(6H,s,CH.sub.3 × 2); 3.45                               (3H,s,NCH.sub.3); 4.2(2H,q,CH.sub.2 CH.sub.3);                                 4.75(1H,q,CHCH.sub.3); 6.85-7.7(6H,                                            m, phenoxy and benzo-ring                                                      protons); 8.1(1H,s, hetero-ring                                                proton).                                                20    Oil    d.sub.6 -acetone                                                                         1.2(3H,t,CH.sub.2 CH.sub.3); 1.6(3H,d,                                         CHCH.sub.3); 3.5(3H,s,NCH.sub.3); 4.2(2H,                                      q,CH.sub.2 CH.sub.3); 5.0(1H,q,CHCH.sub.3);                                    7.3(4H,m, phenoxy ring protons);                                               7.5-8.0(3H,m, benzo-ring                                                       protons); 8.3(1H,s, hetero-ring                                                proton).                                                21    Oil    d.sub.6 -acetone                                                                         1.2(3H,t,CH.sub.2 CH.sub.3); 1.6(3H,d,                                         CHCH.sub.3); 3.6(3H,s,NCH.sub.3); 4.3(2H,                                      q,CH.sub.2 CH.sub.3); 4.8(1H,q,CHCH.sub.3);                                    6.8-7.8(7H,m, phenoxy and benzo-                                               ring protons); 8.3(1H,s, hetero-                                               ring proton).                                           22    Oil    CDCl.sub.3                                                                               1.3(3H,t,CH.sub.2 CH.sub.3); 1.7(3H,d,                                         CHCH.sub.3); 3.6(3H,s,NCH.sub.3); 4.3(2H,                                      q,CH.sub.2 CH.sub.3); 4.9(1H,q,CHCH.sub.3);                                    7.0-8.35(8H,m, aromatic ring                                                   protons).                                               23    97     d.sub.6 -acetone                                                                         1.35(3H,t,CH.sub.2 CH.sub.3); 3.55(3H,s,                                       NCH.sub.3); 4.35(2H,q,CH.sub.2 CH.sub.3); 4.75                                 (2H,s,CH.sub.2 CO); 7.0-8.1(7H,m,                                              phenoxy and benzo-ring protons);                                               8.3(1H,s, hetero-ring proton).                          24    77     d.sub.6 -acetone                                                                         1.3(3H,t,CH.sub.2 CH.sub.3); 1.65(6H,s,                                        C(CH.sub.3).sub.2); 3.55(3H,s,NCH.sub.3);                                      4.3(2H,q,CH.sub.2 CH.sub.3); 6.85-7.9(7H,                                      m, phenoxy and benzo-ring                                                      protons); 8.2(1H,s, hetero-                                                    ring proton).                                           25    74     d.sub.6 -acetone                                                                         1.15(3H,t,CHCH.sub.2 CH.sub.3); 1.3(3H,t,                                      OCH.sub.2 CH.sub.3); 2.1(2H,m,CHCH.sub.2 CH.sub.3);                            1                                                                              3.55(3H,s,NCH.sub.3); 4.35(2H,q,                                               OCH.sub.2 CH.sub.3); 4.65(1H,t,CH); 7.0-                                       7.95(7H,m, phenoxy and benzo-                                                  ring protons); 8.3(1H,s, hetero-                                               ring proton).                                           26    116    d.sub.6 -acetone                                                                         1.65(3H,d,CHCH.sub.3); 3.55(3H,s,                                              NCH.sub.3); 3.85(3H,s,OCH.sub.3); 4.85                                         (1H,q,CHCH.sub.3); 6.9-7.9(7H,m,                                               phenoxy and benzo-ring protons);                                               8.25(1H,s, hetero-ring proton).                         ______________________________________                                    

(b) The intermediates of formula VIII used in the preparation of the compounds of formula I are solids. For convenience, characterising data not already provided in Examples 1 to 13 is recorded in Table 4 below wherein the data refers to the compound of formula VIII used in the preparation of the numbered compound.

                  TABLE 4                                                          ______________________________________                                         Com-                                                                           pound Mp     Proton Chemical Shift                                             No    °C.                                                                            Solvent   δ in ppm                                          ______________________________________                                         13    --     d.sub.6 -acetone                                                                         3.5(3H,s,NCH.sub.3); 7.2(4H,m,                                                 phenoxy protons); 7.8(4H,m,                                                    benzo-ring protons); 8.2(1H,s,                                                 hetero-ring proton).                                    15    206    d.sub.6 -DMSO                                                                            3.5(3H,s,NCH.sub.3); 7.2(4H,m,                                                 phenoxy protons); 7.9-8.7(4H,                                                  m, quinoxaline ring protons).                           16    108    d.sub.6 -acetone                                                                         2.4(3H,s,CH.sub.3); 3.5(3H,s,NCH.sub.3);                                       7.2(4H,m, phenoxy protons);                                                    7.6(3H,m, benzo-ring protons);                                                 8.1(1H,s, hetero-ring proton).                          17    --     d.sub.6 -DMSO                                                                            3.5(3H,s,NCH.sub.3); 7.1(4H,m,                                                 phenoxy protons); 7.7-8.0(3H,                                                  m, benzo-ring protons); 8.1                                                    (1H,s, hetero-ring proton)                              18    --     d.sub.6 -acetone                                                                         2.4(6H,s,CH.sub.3 × 2); 3.5(3H,s,NCH.sub.3);                             6.75-7.75(6H,m, phenoxy and                                                    benzo-ring protons); 8.1(1H,s,                                                 hetero-ring proton).                                    20    179    d.sub.6 -DMSO                                                                            3.4(3H,s,NCH.sub.3); 7.2(4H,m,                                                 phenoxy protons); 7.7-8.2(3H,                                                  m, benzo-ring protons); 8.3(1H,                                                s, hetero-ring proton).                                 22    220    --        --                                                      23-29    See Example 1                                                         ______________________________________                                    

EXAMPLE 15

Concentrated formulations of the compounds of the invention were prepared by:

(a) in the case of oils and waxy solids, dissolving the compound in toluene containing 7% v/v "Teric" N13 ("Teric" is a Trade Mark and "Teric" N13, a product of ethoxylation of nonylphenol, is available from ICI Australia Limited) and 3% v/v "Kemmat" SC15B ("Kemmat" is a Trade Mark and "Kemmat" SC15B is a formulation of calcium dodecylbenzene sulfonate); or

(b) in the case of crystalline solids, adding 5 parts by weight of the compound and 1 part by weight of "Dyapol" PT ("Dyapol" is a Trade Mark and "Dyapol" PT is an anionic suspending agent) to 94 parts by weight of an aqueous solution containing 0.25% v/v of "Teric" N8 (a product of ethoxylation of nonylphenol) and ball-milling the mixture to produce a stable suspension. The emulsifiable concentrates and suspensions were then diluted with water to give an aqueous composition of the required concentration suitable for use in the evaluation of the pre-emergence and post-emergence herbicidal activity of the compounds of the invention.

EXAMPLE 16

The pre-emergent herbicidal activity of the compounds of the invention formulated as described in Example 15 was assessed by the following procedure.

The seeds of the test species were sown in rows 2 cm deep in soil contained in seed boxes. The monocotyledonous plants and the dicotyledonous plants were sown in separate boxes and after sowing the two boxes were sprayed with the required quantity of a composition of the invention. Two duplicate seed boxes were prepared in the same manner but were not sprayed with a composition of the invention and were used for comparison purposes. All the boxes were placed in a glasshouse, lightly watered with an overhead spray to initiate germination and then sub-irrigated as required for optimum plant growth. After three weeks the boxes were removed from the glasshouse and the effect of the treatment was visually assessed. The results are presented in Table 5 where the damage to plants is rated on a scale of from 0 to 3 where 0 represents from 0 to 25% damage, 3 represents 75 to 99% kill and 3+ represents 100% kill. A dash (-) means that no experiment was carried out.

The names of the test plants are as follows:

Wh--Wheat

Ot--Wild Oats

Rg--Ryegrass

Jm--Japanese millet

P--Peas

Ip--Ipomea

Ms--Mustard

Sf--Sunflower

                  TABLE 5                                                          ______________________________________                                         PRE-EMERGENCE HERBICIDAL ACTIVITY                                                    Appli-                                                                   Com-  cation                                                                   pound Rate    Test Plant                                                       No    kg/ha   Wh     Ot  Rg    Jm    P   Ip  Ms   Sf                           ______________________________________                                         1     5       0      0   0     2     0   0   0    0                            1     1       0      0   0     0     0   0   0    0                            6     5       0      0   0     0     0   0   0    0                            6     1       0      0   0     0     0   0   0    0                            17    5       0      0   0     0     0   0   0    0                            17    1       0      0   0     0     0   0   0    0                            21    5       1      1    3+    3+   0   0   0    0                            21    1       0      0   3     3     0   0   0    0                            ______________________________________                                    

EXAMPLE 17

The post-emergent herbicidal activity of the compounds of the invention formulated as described in Example 15 was assessed by the following procedure.

The seeds of the test species were sown in rows 2 cm deep in soil contained in seed boxes. The monocotyledonous plants and the dicotyledonous plants were sown in separate seed boxes in duplicate. The four seed boxes were placed in a glasshouse, lightly watered with an overhead spray to initiate germination and then subirrigated as required for optimum plant growth. After the plants had grown to a height of about 10 to 12.5 cm one box of each of the monocotyledonous plants and the dicotyledonous plants was removed from the glasshouse and sprayed with the required quantity of a composition of the invention. After spraying the boxes were returned to the glasshouse for a further 3 weeks and the effect of treatment was visually assessed by comparison with the untreated controls. The results are presented in Table 6 where the damage to plants is rated on a scale of from 0 to 3 where 0 represents 0 to 25% damage, 3 represents 75 to 99% kill and 3+ represents 100% kill. A dash (-) means that no experiment was carried out.

The names of the test plants are as follows:

Wh--Wheat

Ot--Wild Oats

Rg--Ryegrass

Jm--Japanese millet

P--Peas

Ip--Ipomea

Ms--Mustard

Sf--Sunflower

                  TABLE 6                                                          ______________________________________                                         POST-EMERGENCE HERBICIDAL ACTIVITY                                                   Appli-                                                                   Com-  cation                                                                   pound Rate    Test Plant                                                       No    kg/ha   Wh      Ot    Rg   Jm   P   Ip  Ms   Sf                          ______________________________________                                         1     5        3+     3     3+   3+   0   0   0    0                           1     1       2       3     3+   3+   0   0   0    0                           6     5        3+      3+   3+   3+   0   0   0    0                           6     1        3+      3+   3+   3+   0   0   0    0                           17    5       3        3+   3+   3+   0   0   0    0                           17    1       3       1     2    3+   0   0   0    0                           21    5        3+     2     3+   3+   0   0   0    0                           21    1       2       1     3    3+   0   0   0    0                           ______________________________________                                     

We claim:
 1. A compound of formula I ##STR21## or acid addition salt thereof wherein; A, B, D, E, J, U and V are independently chosen from the group consisting of hydrogen, halogen, nitro, cyano, thiocyano, amino, C₁ to C₆ alkylamino, di(C₁ to C₆ alkyl)amino, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl, C₂ to C₆ alkenyl, C₃ to C₇ cycloalkyl, C₁ to C₆ alkoxy, C₁ to C₆ haloalkoxy, C₁ to C₆ alkylthio, C₁ to C₆ alkylsulfinyl, C₁ to C₆ alkylsulfonyl, C₁ to C₆ haloalkylsulfinyl, C₁ to C₆ haloalkylsulfonyl, sulfo, C₁ to C₆ alkoxysulfonyl, sulfamoyl, N-(C₁ to C₆ alkyl) sulfamoyl, N,N-di(C₁ to C₆ alkyl)sulfamoyl, carboxy, (C₁ to C₆ alkoxy)carbonyl, carbamoyl, N-(C₁ to C₆ alkyl)carbamoyl, N,N-di(C₁ to C₆ alkyl)carbamoyl, phenyl, phenoxy, phenylthio, and the groups substituted phenyl, substituted phenoxy and substituted phenylthio wherein in each group the phenyl ring is substituted with from one to three substituents chosen from the group consisting of halogen, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl, C₁ to C₆ alkoxy, nitro and cyano;R¹ is chosen from the group consisting of hydrogen, C₁ to C₁₀ alkyl, C₂ to C₁₀ alkenyl, C₂ to C₁₀ alkynyl, C₂ to C₁₀ alkoxyalkyl, cyanomethyl, (C₁ to C₆ alkoxy)-carbonylmethyl, C₁ to C₁₀ haloalkyl, formyl, C₂ to C₁₀ alkanoyl, phenyl, benzyl, benzoyl, and the groups phenyl, benzyl and benzoyl wherein in each group the phenyl ring is substituted with from one to three substituents chosen from the group consisting of halogen, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl, C₁ to C₆ alkoxy, nitro and cyano; R² is chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, C₂ to C₆ alkenyl, C₂ to C₆ alkoxyalkyl, C₁ to C₆ haloalkyl, acetyl, propionyl, and C₂ to C₆ alkoxycarbonyl; R³ is chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, C₂ to C₆ alkenyl, C₂ to C₆ alkoxyalkyl and C₁ to C₆ haloalkyl, or R² and R³ together may form a methylene, ethylidene, propylidene or isopropylidene group; W is chosen from the group consisting of cyano, thiocarbamoyl, ##STR22## and CH₂ Z wherein: G is chosen from the group consisting of hydroxy, mercapto, C₁ to C₁₀ alkoxy, C₁ to C₁₀ haloalkoxy, C₂ to C₁₀ alkenyloxy, C₂ to C₁₀ alkynyloxy, C₁ to C₁₀ alkylthio, C₂ to C₁₀ alkenylthio, C₂ to C₁₀ alkynylthio, C₃ to C₇ cycloalkoxy, C₃ to C₇ cycloalkoxy substituted with one or two C₁ to C₄ alkyl groups, phenoxy, phenylthio, benzyloxy, benzylthio, the group C₁ to C₆ alkoxy substituted with a substituent chosen from the group consisting of C₁ to C₆ alkoxy, amino, cyano, N-(C₁ to C₆ alkyl)amino and N,N-di(C₁ to C₆ alkyl)amino, the groups phenoxy, phenylthio, benzyloxy and benzylthio wherein in each group the phenyl ring is substituted with from one to three substituents chosen from the group consisting of halogen, nitro, cyano, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl and C₁ to C₆ alkoxy, the group OM wherein M is an alkali metal ion, alkaline earth metal ion or an ammonium ion N.sup.⊕ R⁷ R⁸ R⁹ wherein R⁷, R⁸ and R⁹ are independently chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, C₁ to C₆ hydroxyalkyl, phenyl and benzyl, the group --NHSO₂ R⁴ wherein R⁴ is chosen from C₁ to C₁₀ alkyl and C₁ to C₁₀ haloalkyl, and the group --NR⁵ R⁶ wherein R⁵ and R⁶ are independently chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, C₁ to C₆ hydroxyalkyl, C₁ to C₆ haloalkyl, phenyl, and benzyl, and the group --O--N═R¹⁰ wherein R¹⁰ is a C₁ to C₁₀ alkylidene group; and Z is chosen from halogen, hydroxy, mercapto, C₁ to C₁₀ alkoxy, C₁ to C₁₀ haloalkoxy, C₁ to C₁₀ alkylthio and the group NR⁵ R⁶ wherein R⁵ and R⁶ are hereinbefore defined; X is chosen from oxygen and sulfur; k is chosen from 0 to 1; 1 is 0; and n is 0, 1 or
 2. 2. A compound according to claim 1 wherein:A, B, D, E, J, U and V are independently chosen from the group consisting of hydrogen, halogen, nitro, cyano, thiocyano, amino, C₁ to C₆ alkylamino, di(C₁ to C₆ alkyl)amino, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl, C₂ to C₆ alkenyl, C₃ to C₇ cycloalkyl, C₁ to C₆ alkoxy, C₁ to C₆ alkylthio, C₁ to C₆ alkylsulfinyl, C₁ to C₆ alkylsulfonyl, (C₁ to C₆ alkoxy)carbonyl, phenyl, phenoxy, phenylthio, and the groups substituted phenyl, substituted phenoxy and substituted phenylthio wherein in each group the phenyl ring is substituted with from one to three substituents chosen from the group consisting of halogen, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl, C₁ to C₆ alkoxy, nitro and cyano; R¹ is chosen from the group consisting of hydrogen, C₁ to C₁₀ alkyl, C₂ to C₁₀ alkenyl, C₂ to C₁₀ alkoxyalkyl, C₁ to C₁₀ haloalkyl, formyl, C₂ to C₁₀ alkanoyl, phenyl, benzyl, benzoyl, and the groups phenyl, benzyl and benzoyl wherein in each group the phenyl ring is substituted with from one to three substituents chosen from the group consisting of halogen, C₁ to C₆ alkyl, C₁ to C₆ halo alkyl, C₁ to C₆ alkoxy, nitro and cyano; R² is chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, C₂ to C₆ alkenyl, C₂ to C₆ alkoxyalkyl, C₁ to C₆ haloalkyl, acetyl, propionyl and (C₁ to C₆ alkoxy)carbonyl; R³ is chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, C₂ to C₆ alkenyl, C₂ to C₆ alkoxyalkyl, and C₁ to C₆ haloalkyl or R² and R³ together form a methylene, ethylidene, propylidene or isopropylidene group; W is chosen from the group consisting of cyano, thiocarbamoyl, ##STR23## and --CH₂ Z wherein: G is chosen from the group consisting of hydroxy, mercapto, C₁ to C₁₀ alkoxy, C₁ to C₁₀ haloalkoxy, C₂ to C₁₀ alkenyloxy, C₂ to C₁₀ alkynyloxy, C₁ to C₁₀ alkylthio, C₂ to C₁₀ alkenylthio, C₃ to C₇ cycloalkoxy, C₃ to C₇ cycloalkoxy substituted with one or two C₁ to C₄ alkyl groups, phenoxy, phenylthio, benzyloxy, benzylthio, the group C₁ to C₁₀ alkoxy substituted with a C₁ to C₆ alkoxy group, the groups phenoxy, phenylthio, benzyloxy and benzylthio wherein in each group the phenyl ring is substituted with from one to three substituents chosen from the group consisting of halogen, nitro, cyano, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl and C₁ to C₆ alkoxy, the group OM wherein M is an alkali metal ion, alkaline earth metal ion or an ammonium ion N⊕R⁷ R⁸ R⁹ wherein R⁷ , R⁸ and R⁹ are independently chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, C₁ to C₆ hydroxyalkyl, phenyl and benzyl, the group --NHSO₂ R⁴ wherein R⁴ is chosen from C₁ to C₁₀ alkyl and C₁ to C₆ haloalkyl, and the group --NR⁵ R⁶ wherein R⁵ and R⁶ are independently chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, phenyl and benzyl; and Z is chosen from halogen, hydroxy, mercapto, C₁ to C₁₀ alkoxy, C₁ to C₁₀ haloalkoxy, C₁ to C₁₀ alkylthio and the group NR⁵ R⁶ wherein R⁵ and R⁶ are independently chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, phenyl and benzyl; X is chosen from oxygen and sulfur; k and l are both 0; and n is 0, 1 or
 2. 3. A compound according to claim 1 wherein:A, B, D and E are independently chosen from the group consisting of hydrogen, halogen, nitro, cyano, amino, C₁ to C₆ alkylamino, di(C₁ to C₆ alkyl)amino, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl, C₂ to C₆ alkenyl, C₁ to C₆ alkoxy, C₁ to C₆ haloalkoxy, C₁ to C₆ alkylthio, carboxy and (C₁ to C₆ alkoxy)carbonyl; J, U and V are independently chosen from the group consisting of hydrogen, halogen, nitro, cyano, C₁ to C₆ alkyl and C₁ to C₆ haloalkyl; R¹ is chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, C₂ to C₆ alkenyl, C₂ to C₆ alkynyl, benzyl, (C₁ to C₆ alkoxy)carbonylmethyl and cyanomethyl; R² is chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, C₂ to C₆ alkoxyalkyl and (C₁ to C₆ alkoxy)carbonyl; R³ is chosen from hydrogen and C₁ to C₆ alkyl; W is chosen from the group ##STR24## and --CH₂ Z wherein: G is chosen from the group consisting of hydroxy, C₁ to C₁₀ alkoxy, C₁ to C₁₀ haloalkoxy, C₂ to C₁₀ alkenyloxy, C₂ to C₁₀ alkynyloxy, C₁ to C₁₀ alkylthio, C₂ to C₁₀ alkenylthio, C₂ to C₁₀ alkynylthio, cyclohexyloxy, phenoxy, benzyloxy, the group C₁ to C₁₀ alkoxy substituted with a substituent chosen from the group consisting of C₁ to C₆ alkoxy, amino, N-(C₁ to C₆ alkyl)amino and N,N-di(C₁ to C₆ alkyl)amino, the group --NR⁵ R⁶ wherein R⁵ and R⁶ are independently chosen from hydrogen, C₁ to C₆ alkyl, C₁ to C₆ hydroxyalkyl, C₁ to C₆ haloalkyl and phenyl, the group OM wherein M is an alkali metal ion, alkaline earth metal ion or an ammonium ion HN⊕R⁷ R⁸ R⁹ wherein R⁷, R⁸ and R⁹ are independently chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, C₁ to C₆ hydroxyalkyl, phenyl and benzyl, the group --NHSO₂ R⁴ wherein R⁴ is C₁ to C₆ alkyl, and the group --O--N═R¹⁰ wherein R¹⁰ is a C₁ to C₁₀ alkylidene group; and Z is chosen from the group consisting of halogen, hydroxy, mercapto, C₁ to C₁₀ alkoxy, and the group --NR⁵ R⁶ wherein R⁵ and R⁶ are independently chosen from the group consisting of hydrogen, C₁ to C₆ alkyl, C₁ to C₆ hydroxyalkyl, C₁ to C₆ haloalkyl and phenyl; X is oxygen; k is chosen from 0 and 1; l is 0; and n is 0 or
 2. 4. A compound according to claim 1 wherein:A, B, D and E are independently chosen from the group consisting of hydrogen, halogen, C₁ to C₆ alkyl, C₁ to C₆ alkoxy, nitro and cyano; J, U and V are independently chosen from hydrogen and halogen; R¹ is chosen from hydrogen and C₁ to C₆ alkyl; R² is chosen from hydrogen and C₁ to C₆ alkyl; R³ is chosen from hydrogen and C₁ to C₆ alkyl; W is the group ##STR25## wherein G is chosen from the group consisting of hydroxy, C₁ to C₁₀ alkoxy, C₂ to C₁₀ alkenyloxy, C₂ to C₁₀ alkynyloxy, C₁ to C₁₀ alkylthio and the group OM wherein M is an alkali metal ion or an alkaline earth metal ion; X is oxygen; k and l are both 0; and n is
 0. 5. A compound according to claim 4 of formula II ##STR26##
 6. A compound according to claim 5 wherein:A, E, J, U and V are hydrogen; B and D are independently chosen from the group consisting of hydrogen, halogen, C₁ to C₆ alkyl, C₁ to C₆ haloalkyl, nitro and cyano; R¹, R² and R³ are independently chosen from hydrogen and C₁ to C₆ alkyl; W is the group ##STR27## wherein G is chosen from the group consisting of hydroxy, C₁ to C₁₀ alkoxy, C₂ to C₁₀ alkenyloxy, C₂ to C₁₀ alkynyloxy, C₁ to C₁₀ alkylthio and the group OM wherein M is an alkali metal ion; X is oxygen; k and l are both 0; and n is
 0. 7. A compound according to claim 6 wherein:A, J, E, U, V and R³ are hydrogen; B and D are independently chosen from the group consisting of hydrogen, halogen, trifluoromethyl, nitro and cyano; R¹ and R² are both methyl; W is the group ##STR28## wherein G is chosen from the group consisting of hydroxy, C₁ to C₆ alkoxy and the group OM wherein M is an alkali metal ion; X is oxygen; k and l are both 0; and n is
 0. 8. A compound according to claim 7 wherein:A, J, E, U, V and R³ are hydrogen; B and D are independently chosen from hydrogen, fluorine, chlorine and bromine; R¹ and R² are both methyl; W is the group ##STR29## wherein G is chosen from the group consisting of hydroxy, C₁ to C₆ alkoxy and the group OM wherein M is sodium or potassium; X is oxygen; k and l are both 0; and n is
 0. 9. A compound according to claim 8 chosen from the group consisting of the methyl, ethyl, n-propyl and isopropyl esters of: 2-{4-[N-methyl-N-(6-chloroquinoxalin-2-yl)amino]phenoxy}propionic acid; 2-{4-[N-methyl-N-(6-bromoquinoxalin-2-yl)amino]phenoxy}propionic acid; 2-{4-[N-methyl-N-(6-fluoroquinoxalin-2-yl)amino]phenoxy}propionic acid; and 2-{4-[N-methyl-N-(6,7-dichloroquinoxalin-2-yl)amino]phenoxy}propionic acid.
 10. A process for selectively controlling the growth of monocotyledonous weeds in dicotyledonous crops which process comprises applying to said crop, or to the growth medium of said crop, a compound as defined according to claim 1 in an amount sufficient to severely damage or kill the weeds but insufficient to substantially damage the crop.
 11. A herbicidal composition comprising as active ingredient a herbicidally effective amount of a compound as defined according to claim 1 and a carrier therefor.
 12. A process for severely damaging or killing unwanted plants which process comprises applying to said plants, or to the growth medium of said plants, an effective amount of a compound as defined according to claim
 1. 13. A process according to claim 12 or claim 10 wherein the compound is applied at a rate in the range from 0.005 to 20 kilograms per hectare. 